A fog generator for a security application is normally technically based on the principle of vaporizing glycol (the fog fluid). Whereby the vaporized fog liquid is emitted into the “area to be fogged” via an outlet channel and a nozzle and immediately condenses into a dispersed aerosol-like fog under atmospheric pressure and room temperature. This fog takes away the criminal's sight and disorients the criminal.
The vaporization (addition of Joules as heat) normally happens via a heat exchanger. The inlet of the heat exchanger is connected to a fog liquid reservoir, whereby the fog liquid is injected by overpressure into the inlet of the heat exchanger at the desired time (fog emission). This overpressure can be generated by:    a) a mechanical pump and/or potential elastic energy (tensioned spring against a piston)    b) operating pressure through compressed or liquid (vapour pressure propellant) propellant, and/or c) operating pressure generated as result of a chemical reaction or a chain reaction.
The fog generation capacity (debit ml/sec) and the fog emission pressure of the heat generator co-depend on the fog fluid supply pressure offered at its inlet and its design.
Depending on the design of the fog generator for security application, it is designated to, if the fog generator housing is under pressure of a compressed or liquid gas, select the cartridge principle. So, WO2003001140 shows a fog generator with a removable housing that comprises a fog generating liquid and a propellant. The fog fluid is entirely injected into the heat exchanger in a single activation. After activation, the cartridge is replaced or a change is made to a second cartridge to obtain an elongated, subsequent or following fog emission.
The most important features of such cartridge are:    1) Comprises the volume of the fog liquid required for a fog emission.    2) Comprises the gas for the operating pressure or a propellant generator (chemical reaction),    3) Comprises a valve so that, upon activation, the fog fluid content is forwarded to the heat exchanger, and    4) Comprises a hydraulic connection to the inlet of the heat exchanger (possibly via a one-way valve, similar or controlled diverter valves).
Prior art fog generators such as, for example, described in WO2003001140, require electrical power that can open the valve (and keep it open or close it again). This power is provided by a (rechargeable) battery or the mains. Being dependent on the mains is naturally unacceptable for security devices. However, the use of a (rechargeable) battery as emergency power source also has a number of disadvantages, as extensively described in application BE2013/0681 and the counterpart, EP13188319.1, both filed on 11 Oct. 2013. An important disadvantage, for example, is the limited service life of such batteries also caused by the high temperature emanating from the heat exchanger in the housing of the fog generator.
Fog generators should, even after years of inactivity, still function well. It was therefore an object of the current invention to further increase the reliability of the fog generators by no longer making the functioning of these devices dependent on an electro-magnetic, mechanical-electric valve or a pump, in which a (rechargeable) battery should substitute as the emergency power supply.